This invention pertains to antennas. More particularly this invention pertains to broad band and multi-band antennas.
Currently in the wireless communication industry there are a number of competing communication protocols that utilize different frequency bands. In a particular geographical region there may be more than one communication protocol in use for a given type of communication e.g., wireless telephones. Also certain communication protocols may be exclusive to certain regions. Additionally future communication protocols are expected to utilize different frequency bands. It may be desirable to provide xe2x80x98future proofxe2x80x99 communication devices that are capable of utilizing a currently used communication protocol, as well as communication protocols that are expected to be utilized in the near future.
It is desirable to be able to produce wireless communication devices capable of operating according to more than one communication protocol. The latter may necessitate receiving signals in different frequency bands. It would be desirable to have smaller antennas for wireless communication devices that are capable of operating at multiple frequencies, rather than having separate antennas for different frequencies.
Some known antennas exhibit peaks in radiative efficiency at frequencies that are harmonics of a base operating frequency. Unfortunately these resonances are likely to be spaced too far apart in frequency, and in any case not at the correct frequencies for communication protocols that are to be supported.
What is needed is an antenna that is capable of operating over a wide frequency range.
Wireless communication devices have shrunk to the point that monopole antennas sized to operate at the operating frequency of the communication device are significant in determining the overall size of the communication devices in which they are used. In the interest of user convenience in carrying portable wireless communication devices, it is desirable to reduce the size of the antenna.
One approach to reducing the overall size of the radiating system of a handheld device is to use a ground plane within the housing of the handheld device, along with a counterpoise that is loaded by a high dielectric constant material, and extends out of the housing as an antenna system. Unfortunately, the hand of a user holding such a handheld device will intercept field lines crossing from the ground plane to the counterpoise and partially block signals passing to and from the antenna system.
What is needed is a small antenna for use in portable wireless communication devices that does not require a large counterpoise.
Commonly wireless phones are equipped with antennas (e.g., wire monopole wire antennas) the radiation patterns of which are independent of azimuth angle. It is desirable to have an antenna that radiates more efficiently within one hemisphere of solid angle about the antenna, in order to achieve higher antenna gain.
What is needed is a more directional antenna that achieves higher antenna gains.
It would be desirable to have a small size antenna that is capable of operating in two or more bands that are widely separated in frequency.